The invention relates to a method and reagent for the determination of peracids, especially for the determination of peracetic acid in the presence of hydrogen peroxide.
Peracetic acid is now increasingly being used for the purposes of disinfection because the resulting reaction products are environmentally acceptable, i.e., acetic acid, water and oxygen. Since the disinfectant activity depends on the concentration of the peracids which decompose with time, repeated assays are important for checking the level of activity of the peracids.
The main problem with assays is that, in addition to acetic acid, aqueous peracetic acid solutions also contain hydrogen peroxide. In most cases, the latter shows similar reactions to peracetic acid so that a determination of the total content of peracetic acid and hydrogen peroxide is obtained by conventional assays, for example, in Anal. Chim. Acta 155, 139 (1983). This determination of the total is, however, not very informative because the disinfectant action derives primarily from the peracetic acid.
Chemical Abstract, vol. 18, 1970, Abstr. 4100, discloses a method for the photometric determination of peracids in the presence of hydrogen peroxide, which is based on the oxidation of m-phenylenediamine by organic peracids at 50.degree.-55.degree. C. and a pH of 2-3 within 30-40 minutes, whereas hydrogen peroxide does not have an oxidative action under these conditions. This method is, in the same way as those which consist of two titrations which have to be carried out successively with different reagents, very time-consuming and requires suitable laboratory equipment and trained laboratory staff.